Messages in this thread | | | From | Andrii Nakryiko <> | Date | Fri, 6 May 2022 17:14:27 -0700 | Subject | Re: [PATCH 4/4] perf record: Handle argument change in sched_switch |
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On Thu, Apr 28, 2022 at 4:58 PM Namhyung Kim <namhyung@kernel.org> wrote: > > On Wed, Apr 27, 2022 at 12:26 PM Andrii Nakryiko > <andrii.nakryiko@gmail.com> wrote: > > > > On Wed, Apr 27, 2022 at 11:15 AM Namhyung Kim <namhyung@kernel.org> wrote: > > > Actually I tried something similar but it was with a variable (in bss) > > > so the verifier in an old kernel rejected it due to invalid arg access. > > > > > > I guess now the const makes the verifier ignore the branch as if > > > it's dead but the compiler still generates the code, right? > > > > > > yes, exactly > > Then I'm curious how it'd work on newer kernels. > The verifier sees the false branch and detects type mismatch > for the second argument then it'd reject the program? >
Verifier will know which branch is never taken, and will just ignore and remove any code in it as dead code.
> Thanks, > Namhyung
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